Method and apparatus for inductively heating valve seats

ABSTRACT

A method and apparatus for simultaneously heating the conical surface of first and second valve seats lying generally in a given plane on an engine component, which method and apparatus comprises mounting two inductors for independent reciprocal and lateral movement with respect to a common frame and biased outwardly therefrom, moving the common frame toward the plane of the valve seats until each is stopped by contacting the engine component, locking the two inductors with respect to the common frame, moving the common frame away from the valve seats to provide the necessary coupling gap, and then energizing the inductors to inductively heat the valve seats preparatory to quench hardening thereof.

[451 Sept. 25, 1973 METHOD AND APPARATUS FOR INDUCTIVELY HEATING VALVESEATS [75 I Inventor: Anthony F. Delpaggio, Parrna, Ohio [73] Assignee:Park-Ohio Industries,C1eve1and,

Ohio

[22] Filed: Dec. 1, 1972 [21] Appl. No.: 311,348

Related US. Application Data [62] Division of Ser. No. 151.493, June 9,1971.

[52] US. Cl 219/l0.57, 219/1043, 219/1071 [51 Int. Cl. H051 35/04 [58]Field of Search 219/1057, 10.75,

[56] Reierences Cited UNITED STATES PATENTS 2,797,289 6/1957 Georgen219/1057 3,696,224 10/1972 Lewis 219/1057 Primary ExaminerR. F. StaublyAssistant ExaminerB. A. Reynolds AttorneyRobert V. Vicker [57] ABSTRACTA method and apparatus for simultaneously heating the conical surface offirst and second valve seats lying generally in a given plane on anengine component, which method and apparatus comprises mounting twoinductors for independent reciprocal and lateral movement with respectto a common frame and biased outwardly therefrom, moving the commonframe toward the plane of the valve seats until each is stopped bycontacting the engine component, locking the two inductors with respectto the common frame, moving the common frame away from the valve seatsto provide the necessary coupling gap, and then energizing the inductorsto inductively heat the valve seats preparatory to quench hardeningthereof.

5 Claims, 14 Drawing Figures PATENTEI] SEP 2 5 I973 SHEET 10F 7 PATENTEU3.761.669

SHEET 30F 7 FIG. 3

fsss

PATENTED3EP25|975 3.761.689 sum nor 7 m re 1 METHOD AND APPARATUS FORINDUCTIVELY HEATING VALVE SEATS This is a division, of application Ser.No. 151,493 filed June 9, 1971.

This invention relates to the art of induction heating and moreparticularly to a method and apparatus for inductively heating the valveseats of an engine component, such as an engine head. v

The invention is particularly applicable for simultaneously heatingadjacent exhaust valve seats of a gray cast iron engine head, and itwill be described with reference thereto; however, it must beappreciated that the invention has broader applications and may be usedfor heating various types of valve seats in engine heads of variousmaterial and for heating similar types of work surfaces.

Internal combustion engines generally employ conical shaped valve seatswhich coact with reciprocal poppet valves for controlling flow of gasesto and from the cylinders. During operation of the engine, the exhaustvalves are subjected to extremely high temperatures and, thus,experience a substantial amount of wear. This wear was reduced bylubricants contained in gasoline, especially lead and phosphorous addedto the gasoline. Recently, g'asolines are being used with reduced leadand/or phosphorous content; therefore, the exhaust valve seats aresubjectedto more rapid deterioration. To counteract this, extensiveefforts have been devoted to increasing the physical properties of theexhaust valve seat during manufacturing.

It has been suggested to heat inductively the conical surface of theexhaust valve seats in an internal combustion engine by using a singleturn inductor positioned adjacent the valve seat, which inductorinductively heats the valve seat preparatory to quench hardening. Thistype of heating installation is extremely well adapted for automaticprocessing of the engine head, since the various exhaust valve seats inan engine head can be inductively heated in a single operation.Consequently, the efforts to improve the physical characteristics of theexhaust valve seats have generally been centered around a gang-typeinduction heating apparatus. These efforts have heretofore takenlvariouscourses. It is necessary toprovide accurate and uniform magneticcoupling between the separate inductors and the'conical surface of thevalve seats. To accomplish this, it has been suggested to bring thevarious inductors into position with respect to the valve seats and thenchange the magnetic coupling at each valve seat by a servo controlledmagnetically permeable core extending through the inductor. Also, it hasbeen suggested to shift the individual inductors with respect to thevalve seats in re sponse to measured magnetic coupling characteristics.All of these efforts have met with limited success.

The present invention relates to a method and appa- 'ratus foraccurately positioning the inductors with respect to the valve seats sothat the induction heating can be uniform without requiringservomechanisms and other individual controls on the separate inductors.

In accordance with the present invention, there is provided an apparatusfor positioning first and second generally circular inductors a common,preselected distance from first and second conical surfaces of a bodymember, which surfaces are to be inductively heated by the inductors.The conical surfaces lie generally in a common planebut may be slightlyoffset therefrom in a direction perpendicular to the plane. Thisapparatus comprises first and second carrier means for supporting eachof the first and second inductors, means for mounting the first andsecond carrier means onto a common frame for independent reciprocalmovement of the carrier means in a direction generally perpendicular tothe plane, means biasing each of the carrier means in a direction towardthe plane and with respect to the common frame, means for moving thecommon frame in a direction generally perpendicular to the plane andtoward the frame until after both of the common carrier means have beenstopped by the body member and have been moved independently of thecarrier frame, means for locking the first and second carrier means ontothe common frame, and means for moving the common frame in a directiongenerally perpendicular to the plane and away from the plane a selecteddistance corresponding to the preselected distance.

In this manner, the two inductors are biased outwardly from a commonframe and the common frame is moved into contact with the body memberwhich may be an internal combustion engine head. This then allows theseparate inductors to seek a common position with respect to the valveseats which they are to heat, preferably in contact with the seats. Thenall of the inductors are locked to the frame, and the frame is movedbackwardly a distance generally corresponding to the desired magneticcoupling distance for the separate inductors. Consequently, noservomechanisms are required, and relatively simple structures areemployed to selectively control the spacing of the individual inductorsfrom their valve seats prior to heating.

In accordance with another aspect of the present invention, there isprovided a method including the steps of providing at least two singleturn inductors having shapes generally matching conical surfaces of thevalve seats, mounting both of these inductors for independent reciprocalmovement with respect to a common frame, biasing each of the inductorstoward the valve seats, moving the common frame toward the valve seatsuntil the engine head stops movement of the individual inductors, thenlocking the inductors onto the common frame, moving the common framebackwardly a preselected distance, and then energizing the inductors toinductively heat the individual valve seats.

In accordance with another aspect of the present invention there isprovided an induction heating device employing a cylindrical secondarywinding secured onto a movable inductor and movable therewith and arelativeby fixed primary winding concentric with the secondary windingand having means for allowing both axial and radial movement between theprimary and secondary windings. By using this concept, slight movementof the inductor, which carries the secondary, can be accommodated in thegap between the primary and secondary windings. Consequently, theprimary winding may be fixedly mounted and without requiring flexibleleads.

In accordance with another aspect of the present invention there isprovided an induction heating device for heating the conical surface ofa valve seat of an engine head preparatory to quench hardening whereinthe engine head has a structural element fixed with respect to thecenter of the conical surface. This device comprises a support framefixed in a direction radial of the conical surface, an inductor having ashape generally matching the conical surface and two input leads forenergizing the inductor, a carrier means for supporting the inductor,means for mounting the carrier means onto the support frame, whichmounting means includes means for limiting movement of the carrier meansto only a direction radial of the conical surface, and means on thecarrier and adapted to coact with the structural element of the head forshifting the inductor to a position with the inductor generallyconcentric with the conical surface.

This particular aspect of the present invention provides a floatinglocator on the inductor at each heating position. This floating locatoris capable of movement only transversely of the valve seat by a supportframe which has means for so limiting the movement of the locator. Inthis manner, if there is a slight misalignment of the inductor as it ismoving toward the valve seat, the locator contacts the engine head andshifts the inductor transversely or radially of the valve seat toprovide concentricity. This movement is relatively limited and can beaccommodated by the previously mentioned relative movement between thesecondary of the transformer, which is fixed to the inductor and theprimary of the transformer which is in a relatively stationary position.

The primary object of the present invention is the provision of a methodand apparatus for inductively heating the conical surface of a valveseat in an internal combustion engine, which method and apparatus isuniform in operation and relatively simple in structure.

Another object of the present invention is the provision of a method andapparatus for inductively heating the conical surface of a valve seat inan internal combustion engine, which method and apparatus provideaccurate control of the magnetic coupling between the inductor and thevalve seat before the inductor is energized.

Still another object of the present invention is to provide a method andapparatus as defined above which do not employ servomotors or selectivecontrols for adjusting the magnetic coupling between the inductor andthe valve seat.

Still another object of the present invention is the provision of alocator device for an inductor to be used to heat inductively theconical surface of a valve seat, which device allows controlled movementof the inductor radial of the valve seat for the purposes of obtainingconcentricity.

Another object of the present invention is the provision of atransformer device for use in an induction heating installation whereinan inductor is moved with respect to the valve seat for the purposes ofobtaining concentricity, which transformer device employs a movablesecondary mounted directly onto the inductor and movable in a radialdirection with respect to a generally fixed primary concentric with saidsecondary.

These and other objects and advantages will become apparent from thefollowing description taken together with the accompanying drawings inwhich:

FIG. 1 is a top plan view illustrating the preferred embodiment of thepresent invention;

FIG. 2 is a side elevational view taken generally along line 2-2 of FIG.1;

FIG. 3 is an enlarged cross-sectional view taken gencrally along line3-3 of FIG. 1;

FIG. 4 is an end view taken generally along line 4-4 of FIG. 3;

FIG. 5 is a top view taken generally along line 55 of FIG. 3; I

FIG. 6 is a partial view taken generally along line 6-6 of FIG. 5;

FIG. 7 is a cross-sectional view taken generally along line 77 of FIG.6;

FIG. 8 is an enlarged partial cross-sectional view taken generally alongline 8-8 of FIG. 1;

FIG. 9 is a partial cross-sectional view taken generally along line 9-9of FIG. 8;

FIG. 10 is a cross-sectional view taken generally along line 10-10 ofFIG. 9;

FIG. 11 is a cross-sectional view taken generally along line ll-ll inFIG. 10;

FIG. 12 is an enlarged cross-sectional view taken generally along linel212 of FIG. 1;

FIG. 13 is a cross-sectional view taken generally along line 13-l3 ofFIG. 12; and,

FIG. 14 is a graph illustrating schematically an operatingcharacteristic of the present invention.

Referring now to the drawings wherein the showings are for the purposeof illustrating a preferred embodiment of the invention only and not forthe purpose of limiting same, FIGS. 1 and 2 show an induction heatingdevice A and an engine head B held in position with respect to theapparatus by appropriate clamping device C, which forms no part of thepresent invention. The engine head includes a plurality of spaced valveseats D generally lying in a common plane and within recessed exhaustports E. Concentric with the conical valve seats are a plurality ofbores F which are adapted to receive the valve stems of a normal poppetvalve. The apparatus A includes, as primary elements, an inductor,inductor carrier and inductor locator device 10, best shown in FIGS.8-11 and hereinafter also referred to as the inductor device; aninductor support and locking device 12, best shown in FIGS. 13, 14; aninductor transformer 14, best shown in FIGS. 3-8; a power input system16, best shown in FIGS. 1 and 2 and somewhat shown in FIGS. 3-7; asupport frame 20 for carrying the above mentioned mechanisms; a platform22 for reciprocally mounting support frame 20; a reciprocating mechanism24, schematically represented as a double acting cylinder fixed onto theplatform 22 and connected to the support frame for reciprocating thesupport frame with respect to the platform; and, back-off mechanism 26.

GENERAL OPERATION Before describing the details of the apparatus A, anoverall general description of the operation thereof will be beneficial.In operation, the engine head B is positioned with the inductor devices10 generally aligned with the respective conical valve seats D.Thereafter, the cylinder 24 moves the support frame 20 forward towardthe engine head. During this forward movement, the respective inductorsof the inductor devices 10 contact the valve seats D so that they areall positioned against the valve seats. To allow this action, each ofthe inductor devices 10 has a biasing arrangement to allow the device tostop when the inductor thereof contacts the valve seat as the supportframe 20 continues forward movement. After all of the inductors are inthe proper position with respect to the individual valve seats, thelocking device 12 locks all of the inductor devices 10 in a fixedposition with respect to the support frame 20. In this manner, allvariations in the spacing of the valve seats and differences in radiallocations thereof are compensated for by the movement of the devices 10.After the locking has been effected, backoff mechanism 26 moves thesupport frame 20 backwardly a distance corresponding to the desiredcoupling gap between the inductors and the valve seats. In practice thisback-off distance is less than 0.060 inches and preferably in thegeneral neighborhood of 0.045 inches which provides a gap of about 0.030inches with the seat surface. After this back-off movement, all of theinductors are in the proper heating position. Thereafter, the inductorsare energized and the valve seats are inductively heated for subsequentquenching by a vehicle or mechanism not forming a part of the presentinvention. It is also contemplated that the seats can be hardened bycooling caused by the mass of the material which requires about 5-7seconds. Thereafter, the inductors can be again energized at a lowerpower level for a short time, such as 3-5 seconds for quenching beforethe head is removed. A variety of structures could be utilized foraccomplishing the above mentioned operation; however, in accordance withthe preferred embodiment of the present invention certain specificstructures are contemplated. These structures will be hereinafterdescribed in detail.

INDUCTOR, INDUCTOR CARRIER AND INDUCTOR LOCATOR DEVICE Referring nowmore particularly to FIGS. 31l, one of the inductor, inductor carrierand inductor locator devices 10, referred to as the inductor devices, isshown in detail. A generally circular, single turn inductor 30 includesconnector leads 32, 34 electrically connected onto a hollow tube 36 anda hollow sleeve 38, respectively. Although the inductor is generallycircular, it can be somewhat elliptical to provide uniform heating. Thetube and sleeve are insulated by sleeves 40, 42. The basic connectorleads for the inductor 30 are, thus, the concentric tube 36 and thehollow sleeve 38. At one end of device there is provided an electricallyinsulated insert 50 which holds the inductor in place and also supportsan outwardly extending tip 52 which includes a cylindrical shaft 54 thatis dimensioned to coact with bore F of the enginehead B. Consequently,as device 10 moves forward, the shaft 54 registers with bore F andshifts the inductor 30 radially into a concentric relationship with thevalve seat D. This necessitates a mechanism for allowing movement of theinductor in a radial direction with respect to the valve seat; how-.ever, a tilting action must be minimized so that the magnetic couplinggap between the inductor and the valve seat will remain uniform aroundthe total circumference of the valve seat. To accomplish this task, andin accordance with the present invention, there is provided anarrangement which will allow the inductor to have slight transversemovement, but a minimum or no tilting action. 1

In accordance with the preferred embodiment of the present invention, amechanism for accomplishing this translation function for the inductorincludes an inductor carrier 60 formed from an insulating material andsecured onto the hollow sleeve 38. The carrier includes an outwardlyextending flange 62 substantially parallel to the general plane of thevalve seat D. Bearing rings 64, 66 are positioned on opposite facingsurfaces of flange 62 to coact with a support frame 70 in a manner to bedescribed.

Referring now to the support frame 70, this frame is mounted onto arearwardly extending sleeve 72 which is, in turn, mounted for onlyreciprocal movement in a mechanism to be described later. Consequently,frame is restrained from movement in a radial direction with respect tothe valve seat D. Frame 70 includes a back plate 74, a cylindricalspacer sleeve 76 and a front, or face, plate 80. A plurality ofcircumferentially spaced clamping bolts 82 are provdied for drawing theface plate toward the back plate. A seal 84 which has sufiicientresiliency to allow movement of the carrier 60 is provided between thecarrier and the face plate 80. Bearing rings 90, 92, similar to bearingrings 64, 66, are secured onto the back plate 74 and the face plate 80,respectively, to provide a bearing surface for ball cages 94, 96. Thesecages provide a series of rolling elements, such as balls, between thebearing ring. A plurality of rubber springs 98 are positioned betweenthe cages and the spacer sleeve 76 to maintain the cages centered. Acontrolled amount of pressure is applied to the balls of the cages 94,96 by the clamping bolts 82 so that movement of the flange 62 can onlybe in a direction substantially parallel to the general plane of thevalve seat D.

. Since it is advisable to center the carrier 60, and thus the inductor30, during each cycle of the apparatus A, there is provided a centeringmeans which may take a variety of structural forms. In accordance withthe preferred embodiment of the present invention, the centering means110 includes a bore 112 in back plate 74 and adapted to receive a camblock 114 having a stern 116 within the bore 112 and an outwardly facinghead I18 having a conical recess 120. Flange 62 is provided with a boregenerally coinciding with the bore 112 in the back plate 74. Within thisbore there is provided a sleeve 132. A ball 134 supported on a carrier136 is reciprocally mounted on the sleeve I32, and is biased toward theconical recess 120 by an appropriate spring 138. This arrangementassures that the carrier 60 is in a preselected position before beingshifted by the bore F. In practice, two of the centering means 110 areprovided on diametrically opposite portions of the device 10. Since theconical recess 120 has a limited active distance a, there isincorporated in the present embodiment an arrangement for limiting theamount of radial shift that can be made by the carrier 60. The limitingarrangement is the radial spacing b between flange 62 and spacer 76.Spacing b is no more than distance a which is the active distance of thecentering means 110. A gap 152 is provided between sleeve 42 and sleeve72. This gap has a dimension 0 which is slightly greater than spacing bso that the sleeve 42 does not contact sleeve 72 during normal operationof the device 10. To limit rotational movement of carrier 60, an element140 includes a bore 142 within back plate 74 and adapted to receive apin 144 which abuts retainer 146 and is held by a press fit. A bore 150within the flange 62 is dimensioned to provide a spacing between the pin144 and the surface of the bore equal to spacing b.

In summary, the inductor device 10 allows the inductor 30 to bepositioned concentrically with respect to the valve seat D without anytilting movement and without actually causing any movment of the supportframe 70 which has an additional function which will be described laterand which is benefitted by the relative flxed position of the supportframe 70 during radial movement of the inductor 30 for the purposes ofconcentricity.

INDUCTOR SUPPORT AND LOCKING DEVICE Referring now to FIGS. 12 and 13,the inductor support and locking device 12 provides for reciprocalmovement of the device supported on sleeve 72 and for locking inductordevice 10 in a reciprocal position determined by the backward movementof the inductor device 10 as it contacts the engine head during forwardmovement of the support frame 20. A variety of structures could be usedfor accomplishing this purpose; however, one structure is schematicallyillustrated and includes a frame 170 for supporting a housing 172.Within the housing there are two axially aligned bearings orbushings174, 176 which reciprocally support sleeve 72. A retainer 180 holdsbushing 174 in position. To prevent rotation of the sleeve 72, there isprovided a key 182 coacting with a keyway 184 in the sleeve. The keylimits movement of the sleeve 72 in both directions. In accordance withthe present invention, the inductor device 10 is biased forwardly towardthe block. In accordance with the illustrated embodiment of the presentinvention this is accomplished by a spring 190 surrounding the sleeve 72and creating a biasing action between bushing 176 and the back plate 74of support frame 70. By this structure, reciprocal movement is allowedand a biasing action is created.

To lock the sleeve 72 in a selected position with respect to housing172, there is provided a locking device 200 which includes a clamp ring202 surrounding the sleeve 72 and having aligned ears 204, 206. The ear206 coacts with a shoulder 208 during the locking op eration. Thelocking action is effected by a cylinder 210 having a rod 212. Ring 202has a ridge 214 that coacts with annular recess 216 to center andlimitthe opening of the ring by its own resiliency.

In operation, when the rod 212 is in the position shown in FIG. 13, theclamp ring 202 is pulled down by a sleeve 220 and locks the sleeve 72with respect to housing 172. The operation of cylinder 210 shifts therod 212 to an upward position so sleeve 220 contacts the upper side ofthe housing. The resiliency of ring 202 opens the ring and releasessleeve 72 for reciprocal movement. The ring is centered by recess 216 toprevent drag on the sleeve 72.

Above the housing 172 there are provided two spaced switches 230, 232and actuators 234, 236 mounted onto the rod 212. These switches are usedto indicate whether the locking device is in the locked or unlockedposition. These switches are used in the electrical circuit for themachine which can take a variety of structural forms and is not a partof the present invention.

INDUCTOR TRANSFORMER AND RELATED STRUCTURE Referring now moreparticlarly to FIGS. 3-8, the inductor transformer 14 and its relatedstructure are illustrated. Basically, insulated bus bars 250, 252 aresupported by an appropriate support structure 352, 354, which does notform a part of the invention, and separated by an insulation 256 areconnected onto hollow, generally parallel input strips 260, 262. Coolanttubes 264, 266 are used to control the temperature of the bus bars.Hollow input strips 260, 262 are directed into the actual transformer270 which is best shown in FIGS. 6 and 7. A single sheet primary 272 isconnected between the strips 260, 262 and includes hollow conductors274, 276. Within the primary winding 272 there are provided a series ofnormal flux concentrators 280. Transformer 270 includes a secondary 290in the form of a single sheet 292 having an axially extending gap 294and terminal ends 296, 298. There is a gap 299 between the primary sheet272 and the secondary sheet 292. This gap has a spacing d, shown in FIG.7, which is at least as great as the spacing b between flange 62 andspacer 76. Consequently, any radial movement of the inductor device 10is allowed by the gap 299.

In accordance with the illustrated embodiment of the invention, thesecondary 290 is cantilevered onto the inductor device 10 by beingcoupled directly onto and supported by the rearwardly extending tube 36and hollow sleeve 38. The connection between the tube and sleeve and thesecondary also forms the electrical connection to these elements forenergizing the inductor 30. A variety of structures could be used formaking this connection; however, in accordance with the illustratedembodiment of the present invention, end 298 of secondary 290 is coupledwith tube 36 by a coupling device 300 best shown in FIGS. 4, 5 and 8.This coupling device includes a block 302 welded onto end 298 and aclamping plate 304 for clamping tube 36 against the block 302. Withinthe block there is a bore 306 having a larger diameter than the diameterof the tube 36 and provided with spaced seals 310, 312 for the coolantsystem to be described later.

Secondary 290 is connected onto sleeve 38 at end 296 by a couplingdevice 320 best shown in FIGS. 5, 6 and 8. A block 322 is welded ontoend 296, and a clamp plate 324 clamps the hollow sleeve 38 with respectto the block 322. Within the block there is provided a bore 326 having adiameter substantially greater than the diamter of the sleeve 38. Spacedseals 330, 332 are provided between the bore 326 and the sleeve 38 for apurpose to be described later.

In summary, the primary and secondary are both single sheets to providea 1:1 ratio. This transformer is primarily utilized for providing arelatively fixed primary and a movable secondary which can be carried bythe inductor itself and can move with respect to the primary asdescribed. This allows for radial adjustment of the inductor withrespect to the valve seat without requiring movement of the primary.

During forward movement of device 10, an arm 340 bolted onto the back ofblock 302 contacts an adjustable switch head 342 which contacts springbiased switch head 344 to indicate forward movement of carrier 22.

POWER SYSTEM Although the power system does not form a part of thepresent invention, it will be described primarily in connection withFIGS. 1 and 2. A normal step-down transformer 350 is supported by andfastened onto frame 20. Output leads 360, 362 are separated by aninsulation member 364 and are connected in series with bus bar sections370, 250, 252, 372, and 374 which connect the inductor transformers 14at positions 1, II, III, and IV in series. The particular bus bararrangement described in connection with the inductor transformer is thearrangement particularly used at position II; however, the remainingconnections are essentially the same and are clearly evident from FIG.1.

TRANSFORMER COOLANT SYSTEM A variety of arrangements could be providedfor cooling the transformer 270; however, in accordance with theillustrated embodiment of the present invention, the primary of thetransformer is cooled by acoolant entering through an inlet 380 whichdirects the coolant through the hollow strip 262 into a pair of passages382 extending through conductors 274, 276. From these passages, acoolant enters passage 384 of hollow strap 260 and then exits from anoutlet 386. The secondary is cooled in a similar manner. Coolant entersthrough an inlet 390 and then flows around a circumferentially extendinghollow conductor 392 to a hollow cross-over conductor 304. From there,the coolant again flows around the secondary sheet 292 in a hollowconductor 396 which directs the coolant to an outlet 398.

INDUCTOR COOLANT SYSTEM In accordance with the present invention, thereis provided a system for cooling the inductor 30. This system, which isbest illustrated in FIGS. 8 and 10, includes an inlet 400 for directinga coolant into a cavity 402 where it is communicated with bore 306 andthen to ports 404 within tube 36. The coolant then flows through passage406 within the tube 36 to lead 32, through this lead, through inductor30, through lead 34 and then to port 410 in the hollow sleeve 38.Coolant then flows through the annular passage 412 to ports 414 whichare in communication with a cavity 416. From the cavity 416, the coolantexits through an outlet 418.

FEEDING AND BACK-OFF MECHANISMS As previously mentioned, cylinder 24moves frame forward to set the inductor devices with the inductors 30 incontact with the respective valve seats F. Thereafter the back-offmechanism 26 is actuated. This mechanism may take various structuralembodiments however, the illustrated embodiment includesa support slide420 for supporting the cylinder 24 and reciprocated on surface 422. Apinion 424 is geared to the slide 420 and is rotated by a rack 426operated by a cylinder 428. A stop 430 is used to limit movement of rack426 and is adjustable with respect to block 432 by a bolt head 434.Consequently, when the frame 20 is being moved by cylinder 24 slide 420is against a shoulder 440. After the inductor devices have been movedback and locked, cylinder 428 actuates rack 426 to shift slide 420 andcylinder 24 backwardly a distance controlled by stop 430. The inductorsare now spaced from the valve seats for heating.

OPERATION OF THE METHOD AND APPARATUS The operation of the method andapparatus has been disclosed r in connection with the separateindividual structures employed; therefore, only a recapitulation of thegeneral method and apparatus is required. An engine head B is positionedas shown in FIGS. 1 and 2 and the locking devices 200 are released sothat the induclateral direction only to bring the inductor 30 intoconcentricity with the valve seat D at each station. Continued movementof the frame 20 brings the indiviudal inductors 30 into contact withtheir respective valve seats. At that time, the frame 20 continuesmovement and devices 10 remain stationary. This changes the relativeposition of the devices 10 with respect to the sup port and lockingdevice 12. After sufficient movement has been made to locate each of theinductors with re spect to their valve seats, the forward movement ofthe frame is stoped. Then the cylinders 210 are actuated to clamp sleeve72 with respect to frame by ring 202. This compensates for any variationin the relative spacing between the respective valve seats. Cylinder 428then moves the frame 20 away from the valve seats a distancecorresponding to the desired gap between the valve seats and theinductors 30. Thereafter, frame 20 is stopped and the heating cycle iscommenced. During lateral adjustment of the respective inductors, thesecondary 290 moves within the primary 272 without contacting the same.This general operation cycle is illustrated in FIG. 15.

In practice the inductors are powered by an oscillator having afrequency between 290450 Kc and each inductor is energized with aboutl0-l 2 kilowatts for about 69 seconds. The inductors are de-energizedfor about 5-7 seconds which allows the mass around the seat to cool theseat and cause hardening. Then, the inductors are again energized by thesame oscillator at a power of about 5 kilowatts for about 3-5 secondsfor tempering. This reduces stresses in the surfaces of the valve seats.

Having thus defined my invention, I claim:

1. A method of simultaneously heating the conical surfaces of first andsecond valve seats lying generally in a given plane in an engine block,said method comprising the following steps:

a. providing first and second single turn inductors having shapesgenerally matching said conical surfaces;

b. mounting both of said inductors for independent reciprocal movementwith respect to a common frame and in a direction generallyperpendicular to said plane;

c. biasing each of said inductors toward said plane;

d. moving said common frame toward said plane with said inductorsgenerally aligned with the conical surfaces of said respective first andsecond valve seats;

e. independently stopping the movment of each of said inductors as itreaches a preselected location closely adjacent to its aligned valveseat while said common frame continues to move toward said plane;

f. thereafter, stopping movment of said common frame in the dirctiontoward said plane; and,

g. energizing said inductors to inductively heat each of said first andsecond valve seats with said respective first and second inductors.

2. The method as defined in claim 1 including the additional steps of:

h. after stopping said common frame, independently locking each of saidinductors with respect to said common frame, and,

i. moving said common frame with said locked inductors in a directionaway from said plane a selected distance before energizing saidinductors, said se- 11 lected distance being no more than the desiredcoupling distance between said valve seat surfaces and said respectiveinductors.

3. The method as defined in claim 2 wherein said selected distance isless than about 0.060 inches.

4. An apparatus for positioning first and second generally circularinductors a common preselected distance from first and second conicalsurfaces of a body member, which surfaces are to be inductively heatedby said inductors and when said conical surfaces lie generally in acommon plane, but may be slightly offset therefrom in a directionperpendicular to said plane,

said apparatus comprising:

a. first and second carrier means for supporting each of said first andsecond inductors;

b. means for mounting said first and second carrier means onto a commonframe for independent reciprocal movement of said carrier means in adirection generally perpendicular to said plane;

c. means biasing each of said carrier means in a direction toward saidplane and with respect to said common frame;

(1. means for moving said common frame in a direction generallyperpendicular to said plane and toward said frame until after both ofsaid carrier means have been stopped by said body member and have beenmoved independently of the common frame;

e means for then locking said first and second carrier means onto saidcommon frame; and,

f. means for then moving said common frame in a direction generallyperpendicular to said plane and away from said plane a selected distancecorresponding to said preselected distance.

5. An apparatus as defined in claim 4 wherein said selected distance andsaid preselected distance are substantially the same.

1. A method of simultaneously heating the conical surfaces of first andsecond valve seats lying generally in a given plane in an engine block,said method comprising the following steps: a. providing first andsecond single turn inductors having shapes generally matching saidconical surfaces; b. mounting both of said inductors for independentreciprocal movement with respect to a common frame and in a directiongenerally perpendicular to said plane; c. biasing each of said inductorstoward said plane; d. moving said common frame toward said plane withsaid inductors generally aligned with the conical surfaces of saidrespective first and second valve seats; e. independently stopping themovment of each of said inductors as it reaches a preselected locationclosely adjacent to its aligned valve seat while said common framecontinues to move toward said plane; f. thereafter, stopping movment ofsaid common frame in the dirction toward said plane; and, g. energizingsaid inductors to inductively heat each of said first and second valveseats with said respective first and second inductors.
 2. The method asdefined in claim 1 including the additional steps of: h. after stoppingsaid common frame, independently locking each of said inductors withrespect to said common frame, and, i. moving said common frame with saidlocked inductors in a direction away from said plane a selected distancebefore energizing said inductors, said selected distance being no morethan the desired coupling distance between said valve seat surfaces andsaid respective inductors.
 3. The method as defined in claim 2 whereinsaid selected distance is less than about 0.060 inches.
 4. An apparatusfor positioning first and second generally circular inductors a commonpreselected distance from first and second conical surfaces of a bodymember, which surfaces are to be inductively heated by said inductorsand when said conical surfaces lie generally in a common plane, but maybe slightly offset therefrom in a direction perpendicular to said plane,said apparatus comprising: a. first and second carrier means forsupporting each of said first and second inductors; b. means formounting said first and second carrier means onto a common frame forindependent reciprocal movement of said carrier means in a directiongenerally perpendicular to said plane; c. means biasing each of saidcarrier means in a direction toward said plane and with respect to saIdcommon frame; d. means for moving said common frame in a directiongenerally perpendicular to said plane and toward said frame until afterboth of said carrier means have been stopped by said body member andhave been moved independently of the common frame; e. means for thenlocking said first and second carrier means onto said common frame; and,f. means for then moving said common frame in a direction generallyperpendicular to said plane and away from said plane a selected distancecorresponding to said preselected distance.
 5. An apparatus as definedin claim 4 wherein said selected distance and said preselected distanceare substantially the same.